The Department of Primary Industries and Regional Development partnered with WA Police to uncover 70 noxious freshwater crayfish in Bunbury and Capel areas.
The highly invasive red swamp crayfish poses an extreme risk to Western Australia's native crustacean species and presents a threat to ecosystems if introduced into local waterways.
It's is a declared noxious species in all Australian States and Territories.
The department and police uncovered the illegal possession and sale of the noxious and non-endemic crustaceans during its Operation Winterfox.
Aquatic Biosecurity Compliance Supervising Fisheries Officer Renee Hilditch said in WA people were not allowed to keep, breed, hatch, culture, possess, consign, convey or release a declared noxious fish and that significant penalties would apply if they did.
"Anyone found in possession of noxious species, such as red swamp crayfish, could face fines up to $10,000 under WA's Fish Resources Management Act 1994," Officer Hilditch added.
"I urge members of the public with any information about red swamp crayfish or other illegal aquarium species to contact the department.
"DPIRD's Aquatic Biosecurity Compliance team is working to educate the community on the need to minimise the risks of noxious fish impacting on WA's aquatic environment."
Red swamp crayfish have the potential to severely impact native freshwater crayfish such as marron, through competition and the introduction of exotic diseases, such as crayfish plague.
Australia is free from crayfish plague, however, if the disease is introduced into WA or Australia, it has the potential to cause large-scale mortalities in many of our freshwater crayfish species and could devastate the freshwater crayfish aquaculture industry.
Red swamp crayfish can range in length from 5-12 cm, their claws and head are elongated and small spines may be present on the sides of its carapace below the head.
They can be dark to light red, with rows of bright red bumps on the front and side of the first leg.
If you think you have seen any red swamp crayfish, or have information about any noxious fish being kept or traded, you can report it anonymously to Fishwatchon 1800 815 507 or send an email to firstname.lastname@example.org.
Never dispose of, or release unwanted or illegal aquarium animals into any waterways or drains.
Dispose of dead aquarium animals by securing them in a plastic bag and placing them in a household rubbish bin for council landfill.